<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=no">
    <link rel="stylesheet" href="css/bootstrap.css">
    <script src="js/jquery-3.6.1.js"></script>
    <script src="js/bootstrap.js"></script>
    <link rel="stylesheet" href="css/my2.css">

</head>
<body>
<div class="container">
    <div class="row">
        <div class="d1 col-xs-4 col-sm-4 col-md-4 col-lg-4"><h1>aaa1</h1></div>
        <div class="d2 col-xs-4"><h1>aaa2</h1></div>
        <div class="d3 col-xs-4"><h1>aaa3</h1></div>
    </div>
</div>

</body>
</html>